Evaluation of a radiolabeled somatostatin analog (I-123 octreotide) in the detection and localization of carcinoid and islet cell tumors

Evidence Base for the Use of PRRT

The development of peptide receptor radionuclide therapy (PRRT) in disseminated neuroendocrine tumors (NETs) has been a long and protracted process. The idea was born within nuclear medicine academia but its translation to clinical practice has been marked by misunderstanding of the rigors of the processes used in drug registration. There were several false starts and some of the required basic science did not occur until after first in man studies. The standard process of preclinical, phase 1, 2 and 3 clinical trials were sometimes blurred and the required data including the assurances that patients were studied on protocol was missing from subsequent publications. Despite this there was a growing conviction and increasing evidence that the use of PRRT had a positive benefit in both survival and symptom relief in about 80% of treated patients. After a decade and a half of false starts and incomplete data a formal randomized controlled trial was conducted comparing PRRT with high dose somatostatin which clearly proved that PRRT was both safe, effective and the treatment of choice in hormone refractory NETs.

Marked 18-Fuorine-Fluorodeoxyglucose (FDG) Avidity of an Intrapulmonary Typical Carcinoid Tumor Manifesting as a Bronchocele in an Asymptomatic Middle-Aged Woman

Patient: Female, 67

Final Diagnosis: Pulmonary carcinoid tumor

Symptoms: Abnormal shadow on Chest X-ray

Medication: —

Clinical Procedure: Surgery – left upper lobe lobectomy

Specialty: Radiology

Somatostatin receptors: from signaling to clinical practice

Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.

Treatment of transplanted tumor of lung adenocarcinoma A549 transfected by human somatostatin receptor subtype 2 (hsstr2) gene with 188Re-RC-160

BACKGROUND AND AIM

Radionuclide-labeled somatostatin analogues selectively target somatostatin receptor (SSTR)-expressing tumors as a basis for diagnosis and treatment of these tumors. To those tumors without somatostatin receptor expressed, the hSSTR2 gene was transfected. Express of the hSSTR2 receptor was imaging and the radiotherapeutic effect was evaluated with (188)Re-RC-160.

METHODS

The stable hSSTR2-expressing A549 cells (pcDNA3-hSSTR2 A549) and non-somatostatin receptor expressing A549 cells (pcDNA3 A549) were selected by western blot. Later, a corresponding animal tumor model was established. Expression of the hSSTR2 reporter was imaged using (188)Re-RC-160 recognition. Tumors were evaluated for somatostatin receptor expression using immunohistochemistry. The distribution of (188)Re-RC-160 in the animal tumor model was measured and the inhibitory effects of (188)Re-RC-160 were evaluated by measurement of tumor growth and hematoxylin and eosin and TdT mediated dUTP nick end labeling (TUNEL) staining.

RESULTS

In vivo radioimaging revealed specific targeting of (188)Re-RC-160 to tumors derived from pcDNA3- hSSTR2 A549 cells, compared to those from pcDNA3 A549 cells. pcDNA3- hSSTR2 A549 tumor growth inhibition was significantly higher in the single 7.4 MBq (188)Re-RC-160 treatment group than in the 2×7.4 MBq rhenium-188, RC-160 group, control group, and pcDNA3 A549 tumors (P<.05). Furthermore, treatment fractionation group (2 × 7.4 MBq (188)Re-RC-160), induced significantly increased tumor-growth inhibition compare with single 7.4 MBq (188)Re-RC-160 treatment (P<.05).

CONCLUSION

These studies showed that (188)Re-RC-160 could be effectively used for targeting therapy the A549-derived tumors exogenously expressing hSSTR2, which will offers a potential therapeutic strategy for the treatment of somatostatin receptor-negative cancers.

Epidemiological study of gastroenteropancreatic neuroendocrine tumors in Japan

BACKGROUND

There have been few epidemiological studies on gastroenteropancreatic neuroendocrine tumors (GEP-NETs) in Japan.

METHODS

We examined the epidemiology of GEP-NETs [pancreatic endocrine tumors (PETs) and gastrointestinal neuroendocrine tumors (GI-NETs)] in Japan in 2005 using a nationwide stratified random sampling method.

RESULTS

A total of 2,845 individuals received treatment for PETs. Prevalence was estimated as 2.23/100,000 with an annual onset incidence of 1.01/100,000. Non-functioning tumor (NF)-PET constituted 47.4%, followed by insulinoma (38.2%) and gastrinoma (7.9%). Distant metastases were reported in 21% patients with NF-PETs and occurred more frequently as tumor size increased (>2 cm). Multiple endocrine neoplasia type 1 (MEN-1) was detected in 10% of PETs but only in 6.1% of NF-PETs. NF-PETs were detected incidentally by physical examination in 24% patients. In 2005, an estimated 4,406 patients received treatment for GI-NETs. Prevalence was estimated as 3.45/100,000, with an annual onset incidence of 2.10/100,000. The locations of GI-NETs varied: foregut, 30.4%; midgut, 9.6%; and hindgut, 60.0%. Distant metastases were observed in 6%. Lymph node metastases occurred more frequently as tumor size increased (>1 cm). The frequency of MEN-1 complications was 1%. Physical examination revealed GI-NETs in 44% patients. The frequency of symptomatic GI-NETs was 3.4%. Interestingly, 77.1% of patients with foregut GI-NETs had type A gastritis.

CONCLUSION

Our results show there are large differences in GEP-NETs between Japan and Western nations, primarily due to differences in the presence of MEN-1 in NF-PETs and the location, symptomatic status, and prevalence of malignancy in GI-NETs.

Correlation of chromogranin A levels and somatostatin receptor scintigraphy findings in the evaluation of metastases in carcinoid tumors

OBJECTIVE

Chromogranin A (CgA) has been gaining acceptance as a helpful tumor marker in patients with neuroendocrine tumors, with respect to both diagnosis and prognosis. The objective of this study was to correlate serum CgA levels and somatostatin receptor scintigraphy (SRS) findings in the evaluation of metastases in carcinoid tumors.

MATERIALS AND METHODS

A total of 125 patients(61 men and 64 women, aged from 23 to 84 years) with histologically diagnosed carcinoid tumor underwent serum CgA assay and SRS for detecting metastasis or disease recurrence. The quantitative determination of CgA was performed in serum using an enzyme immunoassay with a cut-off value fixed at 39 U/l. Scintigraphies were performed with 200-220 MBq of In-111-DTPA-Phel-octreotide including whole-body images as well as single-photon emission computed tomography and computed tomography scans of the chest and abdomen.

RESULTS

The primary tumors originated from the gastrointestinal tract in 115 of 125 patients (92.0%), the lung in 7 of 125 patients (5.6%), the kidney in 2 of 125 patients (1.6%), and the breast in 1 of 125 patients (0.8%). The primary tumors originated from the foregut, midgut, and hindgut in 13.6%, 71.2%, and 12.8%, respectively. Correlation of SRS with other imaging modalities and clinical follow-up findings revealed a sensitivity, a specificity, and an accuracy of 82.9%, 97.7%, and 88.0%, respectively, and for CgA 62.2%, 83.7%, and 69.6%, respectively. There was 1 false-positive and 14 false-negative SRS results and 7 false-positive and 31 false-negative CgA analyses. SRS demonstrated higher sensitivity, specificity, and accuracy than CgA for the evaluation of metastatic carcinoid tumors. The concordance between SRS and CgA results was 67.2%. Discrepancies, such as positive SRS with normal CgA levels, were noted in 26 (20.8%) cases, whereas negative SRS with high CgA levels was seen in 15 (12.0%) cases. Combining the results of CgA and SRS increased the sensitivity (92.7%) but decreased the specificity (81.4%) of tumor detection.

CONCLUSIONS

In our study, SRS proved to be more sensitive, more specific, and more accurate than CgA for metastatic evaluation of carcinoid tumors. Positive SRS correlated with elevation of serum CgA levels. Serum CgA might have some diagnostic utility in patients with negative SRS studies. Nevertheless, both SRS and CgA should be considered useful tools in the evaluation of metastases in carcinoid patients.

Emerging therapies for the treatment of patients with advanced neuroendocrine tumors

Patients with neuroendocrine tumors may pursue a number of treatment options, but there is little consensus on a single, standard treatment approach. Somatostatin analogs are generally administered to patients with symptoms of hormonal secretion, and are often highly effective in this regard. However, the administration of somatostatin analogs is only rarely associated with tumor regression, and randomized trials demonstrating a survival benefit associated with their use have not been performed. Selected patients with hepatic metastases may undergo surgical debulking, embolization or other ablative therapies. The clinical benefit associated with administration of systemic agents such as IFN-alpha or cytotoxic chemotherapy has been limited. With the possible exception of streptozocin-based therapy in patients with pancreatic neuroendocrine tumors, the widespread use of standard cytotoxic regimens has been limited by their relatively modest antitumor activity, as well as concerns regarding their potential toxicity. The modest efficacy seen with these agents in patients with advanced neuroendocrine tumors has led to great interest in the development of novel treatment approaches. One such approach is the use of radiolabeled somatostatin analogs. Recently, agents targeting the VEGF pathway and mammalian target of rapamycin have also shown promise in patients with advanced neuroendocrine tumors. Ongoing randomized studies should help better define the role these agents will play in the future treatment of patients with this disease.

Role of radiolabeled octreotide therapy in patients with metastatic neuroendocrine neoplasms

Peptide receptor radionuclide therapy is a new therapeutic modality for patients with nonresectable neuroendocrine tumors. The technique is based on the unique ability of these tumors to express cell membrane-specific peptide receptors that can be targeted with radiolabeled somatostatin analogues. A high level of uptake on somatostatin receptor scintigraphy is a prerequisite for effective treatment. The efficacy of this method has been proven in several clinical trials. In a substantial number of patients, an improvement of life quality has been achieved in addition to a marked morphologic and biochemical tumor response. Serious side effects are rarely observed. Attention must be paid to kidney protection during the treatment. The present review summarizes the clinical experience with the treatment of advanced neuroendocrine tumors with radiolabeled somatostatin analogues and focuses on patient selection and the appropriate timing of the therapy. Finally, it emphasizes treatment-related issues that deserve attention in the future.

Clinical Presentation and Management of Carcinoid Tumors

The generally indolent nature of neuroendocrine tumors is an advantage in the management of patients who have localized disease, and surgery alone is often curative. This same property presents a challenge in the treatment of patients who have metastatic disease, in whom standard cytotoxic chemotherapy has a limited benefit. In such patients, the use of somatostatin analogs, interferon, and the treatment of hepatic metastases may provide effective palliation. The highly vascular nature of carcinoid tumors has led to the investigation of antiangiogenic agents in this setting. Preliminary reports of activity associated with agents targeting the vascular endothelial growth factor pathway suggest that such strategies may play a role in the future treatment of patients who have this disease.

Preliminary results of a Japanese nationwide survey of neuroendocrine gastrointestinal tumors

BACKGROUND

We conducted a nationwide survey to estimate the incidence of neuroendocrine gastrointestinal tumors (NETs) newly diagnosed in Japan from 2002 through 2004.

METHODS

Data on 1541 patients, 514 pancreatic endocrine tumors (PETs) and 1027 gastrointestinal carcinoids (GICs), were collected and analyzed.

RESULTS

Nonfunctioning tumors (NF-PET) constituted 47.7% of PETs. Next in frequency were insulinoma (31.7%) and gastrinoma (8.6%). Malignancy was frequent in NF-PETs (46.1%) and gastrinomas (45.5%), but only 7.4% of insulinomas were malignant. The incidence of multiple endocrine neoplasia type-1 associated with PETs was 7.4%. The incidence of GICs was 28.8%, 5.2%, and 66.0% in foregut, midgut, and hindgut, respectively. Carcinoid syndrome and metastases were observed in only 1.7% and 5.6% of GICs, respectively.

CONCLUSIONS

The incidence of NETs in Japan was clarified by this preliminary study. Comparatively large differences in GICs between Japan and Western nations were present with regard to the location, symptomatic status, and prevalence of malignancy.

213Bi-[DOTA0, Tyr3]Octreotide Peptide Receptor Radionuclide Therapy of Pancreatic Tumors in a Preclinical Animal Model

PURPOSE

The somatostatin analogue [DOTA0, Tyr3]octreotide (DOTATOC) has previously been labeled with low linear energy transfer (LET) beta-emitters, such as 177Lu or 90Y, for tumor therapy. In this study, DOTATOC labeled with the high-LET alpha-emitter, 213Bi, was evaluated.

EXPERIMENTAL DESIGN

The radiolabeling, stability, biodistribution, toxicity, safety, and therapeutic efficacy of 213Bi-DOTATOC (specific activity 7.4 MBq/microg) were investigated. Biodistribution studies to determine somatostatin receptor specificity were done in Lewis rats at 1 and 3 hours postinjection. Histopathology of various organs was used to evaluated toxicity and safety. Therapeutic efficacy of 4 to 22 MBq 213Bi-DOTATOC was determined in a rat pancreatic carcinoma model.

RESULTS

Radiolabeling of the 213Bi-DOTATOC was achieved with radiochemical purity >95% and an incorporation yield > or = 99.9%. Biodistribution data showed specific binding to somatostatin receptor-expressing tissues. Administration of free 213Bi, compared with 213Bi-DOTATOC, resulted in higher radioactivity accumulation at 3 hours postinjection in the kidneys [34.47 +/- 1.40% injected dose/g (ID/g) tissue versus 11.15 +/- 0.46%, P < 0.0001] and bone marrow (0.31 +/- 0.01% ID/g versus 0.06 +/- 0.02%, P < 0.0324). A significant decrease in tumor growth rate was observed in rats treated with >11 MBq of 213Bi-DOTATOC 10 days postinjection compared with controls (P < 0.025). Treatment with >20 MBq of 213Bi-DOTATOC showed significantly greater tumor reduction when compared with animals receiving <11 MBq (P < 0.02).

CONCLUSIONS

213Bi-DOTATOC showed dose-related antitumor effects with minimal treatment-related organ toxicity. No acute or chronic hematologic toxicities were observed. Mild, acute nephrotoxicity was observed without evidence of chronic toxicity. 213Bi-DOTATOC is a promising therapeutic radiopharmaceutical for further evaluation.

Nuclear medicine in the detection and management of pancreatic islet-cell tumours

Over the last decade somatostatin receptor scintigraphy using various derivatives of long-acting somatostatin analogues has gained its place in the management of pancreatic islet-cell tumours. Scintigraphy is based on the high-affinity binding of such somatostatin analogues to receptors over-expressed by these tumour types. Following the introduction of (111)In-DTPA-D-Phe(1)-octreotide, clinical studies with radiolabelled DOTA-Tyr(3)-octreotide and DOTA-Tyr(3)-octreotate derivatives have shown considerable improvement of imaging results with increased tumour uptake. One of the newer developments, (68)Ga-labelled DOTA-Tyr(3)-octreotide, has shown promising results in patients with pancreatic islet-cell tumours, based on the high-affinity binding to the somatostatin receptor subtype 2 in combination with positron emission tomography (PET) technology. Other peptides--such as ligands for the gastrin/CCK2 receptors or vasoactive intestinal peptide (VIP)--have also been studied for imaging pancreatic cell tumours. Whereas small-sized gastrinoma, somatostatinoma, glucagonoma, carcinoid and VIPoma are frequently detected by somatostatin receptor scintigraphy, insulinoma may escape detection due to reduced receptor expression. Following peptide receptor scintigraphy, a change in patient management is reported in up to 30% of patients. When labelled with (90)Y or (177)Lu, some somatostatin analogues have been applied to patients in advanced stages of the disease. Despite positive response data in 50% of patients, long-term results and survival rates are lacking.

Small bowel tumors

Primary tumors of the small bowel are rare, and their clinical presentation is nonspecific. Consequently, preoperative diagnosis remains the exception rather than the rule. Although the small intestine makes up 75% of the length and 90% of the surface area of the gastrointestinal tract, small bowel tumors make up approximately 3% of all malignant gastrointestinal neoplasms. Primary neoplasms of the small intestine are notorious for their insidious presentation and vague symptoms, including abdominal pain, anorexia, and weight loss. These nonspecific symptoms, coupled with the lack of physical findings, often cause a significant delay in reaching a diagnosis. Because the small bowel has been a relatively inaccessible area to standard endoscopic techniques, contrast radiography has been regarded historically as the gold standard diagnostic modality. The management of primary malignant small bowel tumors is invariably surgical. However, adjuvant chemotherapy and radiotherapy may be warranted, depending on the type of tumor.

Somatostatin analog therapy in treatment of gastrointestinal disorders and tumors

Long-acting octapeptide somatostatin analogs can effectively control symptoms resulting from excessive hormone release in patients with endocrine tumors of the gastrointestinal tract, provided that these tumors and metastases show a high expression of the somatostatin receptor subtype 2. The presence of this receptor subtype on these tumors can be demonstrated by in vitro studies, but also in vivo using 111In-pentetreotide scintigraphy. In a few studies, significant antiproliferative effects of these drugs on these tumors have also been demonstrated. The effectiveness of octapeptide somatostatin analogs in the management of chemotherapy- related and AIDS-related diarrhea and in reducing postoperative complications of pancreatic surgery have also been demonstrated. These drugs have been used to decrease the output of enterocutaneous pancreatic fistulas and are prophylactically used to prevent the development of these fistulas. Octapeptide somatostatin analog therapy is widely accepted for the initial management of acute variceal bleeding in cirrhotic patients. These drugs are currently also being evaluated for the treatment of advanced hepatocellular carcinoma and malignant intestinal obstruction. Radiotherapy with octapeptide somatostatin analogs coupled to radionuclides such as indium-111, yttrium-90, and lutetium- 177 is currently being studied in phase I-III trials.

Unusual primary lung neoplasms

Bronchial carcinoids and hamartomas are, respectively, the most common malignant and benign unusual primary lung neoplasms. These tumors are often asymptomatic but can cause central airway obstruction. Helical computed tomographic and radionuclide scintigraphic advances in their detection and evolution, together with newer interventional bronchoscopy techniques such as neodymium:yttrium-aluminum-garnet laser phototherapy and cryotherapy, represent important improvements in the diagnosis and management of patients with such tumors.

[Endocrine tumors of the duodenum and pancreas: "prerequisites", imaging, and intraoperative detection]

Non-secreting pancreatic neuroendocrine tumors and diarrheogenic tumors are usually bulky and easy to recognize thanks to somatostatin-receptor scintigraphy and hormonal dosages. The real difficulty concerns insulinomas and particularly gastrinomas, which are found at the level of the duodenum and can be very small. Diagnosis is based on biological examinations, and the search for MEN I must be done systematically. Their localization is based on two essential and noninvasive exams: echoendoscopy and somatostatin-receptor imaging, though the surgeon's skill in the operative field, aided by an intraoperioperative echography, is indispensable. Surgical treatment of insulinomas gives excellent results. However, for sporadic gastrinomas, there was only a 34% recovery rate, and still less for MEN I gastrinomas.

Scintigraphic diagnosis of insulinoma in a dog

Diagnosis of insulin-secreting tumors of the pancreas can usually be made on the basis of endocrine testing and exclusion of other causes of hyperinsulinism. In dogs, these tumors have a poor long-term prognosis due to a high rate of metastases and recurrence; staging (and therefore prognosticating) is difficult and usually done at the time of surgery. The purpose of this article is to describe a canine patient with an insulinoma, discuss the diagnostic imaging options for tumor evaluation and mention future directions for therapy. Insulinoma was suspected in an 8-year-old intact male Irish Setter. Somatostatin receptor scintigraphy using indium In-111 pentetreotide was performed and an area of increased radiopharmaceutical accumulation was found craniomedial to the right kidney. At surgery a small mass lesion in the pancreas and a larger, closely associated mass involving a mesenteric lymph node were removed. Histopathology confirmed the diagnosis of insulinoma with regional lymph node metastasis. The dog recovered from surgery and remained normal fourteen months later.

Noninvasive imaging of insulinomas and gastrinomas with endoscopic ultrasonography and somatostatin receptor scintigraphy

BACKGROUND

Classic morphological techniques are of limited value for imaging endocrine duodenopancreatic tumors, and invasive procedures such as intraarterial stimulation are often used. Two noninvasive procedures, endoscopic ultrasonography (EUS) and somatostatin receptor scintigraphy (SRS), were recently described with promising results.

METHODS

In this study we correlated the results of preoperative EUS (n = 34) and SRS (n = 30) with operative findings in patients with histologically proven insulinoma (n = 20) or gastrinoma (n = 21).

RESULTS

The sensitivity and positive predictive value (PPV) of EUS were respectively 77% and 94% for pancreatic tumors (insulinomas and gastrinomas), 40% and 100% for duodenal gastrinomas, and 58% and 78% for metastatic lymph nodes. The sensitivity and PPV of SRS for insulinoma were 60% and 100%, respectively. In patients with gastrinoma, the sensitivity and PPV of SRS were respectively 25% and 100% for pancreatic gastrinomas, 72% and 100% for duodenal gastrinomas or periduodenal metastatic lymph nodes, and 67% and 80% for liver metastasis. In patients with multiple endocrine neoplasia, neither one of the two techniques detected all tumors. Overall sensitivity of combined EUS and SRS was 89% for insulinoma (n = 9) and 93% for gastrinoma (n = 14).

CONCLUSIONS

EUS and SRS for gastrinomas and insulinomas should be considered as the initial preoperative imaging procedures and may render invasive procedures unnecessary for most patients.

Somatostatin-receptor-negative carcinoid tumour responsible for Cushing's syndrome

A 30-year-old man presenting with Cushing's syndrome was admitted in 1995. A diagnosis of ectopically ACTH-secreting, primary-unknown abdominal carcinoid tumour was made. The patient's plasma ACTH and cortisol levels failed to decrease after short-term treatment with octreotide, and somatostatin-receptor scintigraphy did not show any accumulation in the tumour. The patient died 1 year after admission. This is a relatively rare somatostatin-receptor-negative case of this disease and it appears necessary to test for the presence of somatostatin receptors before treating with octreotide.

Insulinoma: a review of current management

Insulinomas are a relatively rare tumour which occur predominantly in the pancreas. The majority of the tumours are benign, but have profound effects upon the patient. The diagnosis of insulinoma is often elusive, and the management may involve demanding surgery with a significant morbidity. In this review article, all clinical aspects of insulinomas are examined. Particular emphasis is placed on the myriad modes of presentation, and the methods used to localise the tumour pre-operatively. Medical, as well as surgical treatments are discussed and their role in the management of both malignant and benign tumours. Despite potential difficulties encountered in managing patients with this tumour, a large majority may be either cured or achieve useful palliation.

Evaluation of somatostatin analogues for the detection and treatment of gastrinoma in a dog

Gastrinomas in dogs are difficult to diagnose, localise and treat. In humans, somatostatin analogues have improved localisation and treatment of gastrinomas. The somatostatin analogues pentetreotide and octreotide were evaluated for the detection and treatment of gastrinoma in a dog. 111indium-pentetreotide scintigraphy revealed multiple areas of activity in the patient's mid-ventral abdomen which were consistent with masses in the pancreas and liver at laparotomy. Immunohistochemistry, electron microscopy and binding of 125I-[Tyr3]-octreotide in vitro confirmed the lesion as a gastrinoma which expressed somatostatin receptors. Octreotide at doses of 2, 4 and 8 micrograms/kg caused transient decreases in circulating gastrin. Plasma somatostatin peaked at one hour after octreotide and was still detectable at four and six hours after administration of octreotide. Combination therapy with famotidine, omeprazole, sucralfate and increasing doses of octreotide allowed patient survival for 14 months.

CT of pancreatic neoplasms. Part II: The unusual tumors

The pancreas gives rise to a remarkable variety of neoplasms other than ductal adenocarcinoma. Although no individual type of tumor in this category is prevalent enough to qualify as common, most types are currently encountered with a frequency far greater than that in decades of the recent past. This change is largely the result of the expanded use of contemporary abdominal imaging. The unusual tumors of the pancreas vary greatly in their biologic behavior and, accordingly, in their clinical consequences and therapeutic requirements. Accurate diagnosis, therefore, can be of considerable clinical relevance. Not only is it worthwhile to distinguish one type of unusual pancreatic tumors from another, it is perhaps of even greater consequence to distinguish the unusual tumors from ordinary pancreatic adenocarcinomas. The goals of this discussion are to expand radiologic awareness of these uncommon but interesting pancreatic neoplasms and to increase familiarity with their diagnostically salient features.

New trends in nuclear oncology: current problems in diagnosis of neoplastic diseases

The diagnosis of oncologic diseases requires four levels of imaging intervention: identification, characterization, staging, and follow-up. Diagnostic problems in the identification of neoplastic disease may be present both for screening and for symptomatic patients; until today, few screening studies have been organized (e.g., screening for carcinoma of cervix); the realization of similar programs for other kinds of neoplastic disease could be useful. In the characterization of neoplastic masses, imaging signs are often pathognomonic. Moreover, the approach with imaging-guided biopsy is often diagnostic. In some cases, interventional radiologic procedures are not indicated, and only the integration of radiologic techniques like spiral CT and/or MRI with techniques of nuclear-medicine such as positron emission tomography (PET) can tackle the problem. Problems concerning the staging and/or restaging of neoplasms are even more complex: In general terms, radiologic imaging is, in our opinion, a good way to solve problems about local staging (T), whereas it seems to be less accurate in detecting distant small lesions (M), neoplastic lymph nodes (N), or in distinguishing fibrous tissue after therapy (chemo, surgical or radiotherapy) from neoplastic relapse. This paper describes the usefulness of integrated research in oncology between radiologic and functional imaging.

Positive somatostatin receptor scintigraphy correlates with the presence of somatostatin receptor subtype 2

Somatostatin receptor scintigraphy (SRS) is positive in approximately 75% of all patients with neuroendocrine gastroenteropancreatic tumours. This study aimed to identify specific somatostatin receptor (sstr) subtypes, which are responsible for the in vivo binding of the widely used somatostatin analogue, octreotide in human neuroendocrine gastroenteropancreatic tumours. Twelve patients underwent SRS with radiolabelled octreotide. After surgical resection, tumour tissues were analysed in vitro for somatostatin and octreotide binding sites by autoradiography. In addition, for the first time, sstr subtype mRNA expression was examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Tumour tissues from all SRS positive patients were positive by autoradiography. Semiquantitative RT-PCR revealed most prominently sstr2 expression in scintigraphically positive tumours. Two SRS negative tumours contained in vitro octreotide binding sites as well as high levels of sstr1 and sstr2 mRNAs. Positive SRS is mainly due to sstr2. sstr1, 3, 4, and probably 5 are less important for in vivo octreotide binding. False negative scintigraphic results seem to be influenced by factors independent of the expression of specific sstr.

Indium-111-pentetreotide scanning versus conventional imaging techniques for the localization of gastrinoma

BACKGROUND

The present study evaluates 111In-pentetreotide scanning as a method for detection of gastrinomas. Operative findings serve as the benchmark for comparison of the efficacy of 111In-pentetreotide versus conventional imaging studies.

METHODS

Twelve patients (seven female and five male; age, 37 to 80 years) with histologic confirmation of gastrinoma underwent thin section dynamic computed tomography (CT) scanning and 111In-pentetreotide scanning. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 111In-pentetreotide and CT scanning are compared on the basis of tumor size and location.

RESULTS

Thirty discrete foci of intrahepatic and extrahepatic tumors were detected at operation. CT scanning detected three of nine pancreaticoduodenal lesions, whereas eight of these nine extrahepatic primary tumors were imaged by 111In-pentetreotide scanning. No false-positive 111In-pentetreotide scans were noted. The sensitivity of CT scanning for detection of metastatic disease was 56% versus 94% for the 111In-pentetreotide scan. Successful CT imaging was highly dependent on tumor size. No tumor smaller than 1 cm was imaged by CT, whereas four of seven lesions greater than 1 cm were imaged by 111In-pentetreotide scintigraphy. The smallest gastrinoma imaged by 111In-pentetreotide scanning was a 4 mm duodenal tumor.

CONCLUSIONS

111In-pentetreotide scanning was superior to CT scanning for localizing gastrinomas. Further studies are required to determine whether 111In-pentetreotide scans will complement or replace traditional imaging methods.

Nuclear imaging of solid hepatic masses

This review has focused on the unique role of radionuclide scintigraphy in characterization of hepatic mass lesions. Radionuclide scintigraphy, unlike most other imaging modalities, is based on specific physiological and biochemical properties of each pathological entity that affects the liver. Hepatic scintigraphy, with its widespread availability, noninvasive nature, and relatively low cost is a powerful adjunct to other imaging techniques in the investigation of hepatic mass lesions. We have reviewed clinical presentation and characteristic findings of most hepatic lesions and have described reported findings with all available imaging modalities with particular emphasis on hepatic scintigraphy (Table 1) as well as a suggested algorithm for workup of solid hepatic masses (Fig 6). Additionally, the role of newer, more specialized techniques including PET scanning, 123I-labeled VIP, and 111In-labeled DTPA-D-Phe-octreotide scanning are reviewed. Hepatic nuclear scintigraphy continues to play an important role in the management of patients with solid hepatic masses.

Advances in the management of patients with Zollinger-Ellison syndrome

A detailed description of recent advances in the management of patients with Zollinger-Ellison syndrome (ZES) is presented. The clinical presentation is reviewed, and newer diagnostic tools, both preoperative and intraoperative, are discussed. An update on surgical management is presented, including indications for abdominal exploration, intraoperative localization techniques, surgical excision, and the approach to patients with metastases or in whom no tumor is found. New strategies in the medical management of ZES also are reviewed. An update on patient survival is presented, and a review of the management of patients with multiple endocrine neoplasia type 1 and ZES is discussed.

Neoplastic lesions of the appendix

Neoplasms occur in 0.5 per cent of appendices. Ultrasonography or computed tomography is beneficial, but preoperative detection is rare. At operation, the diagnosis is considered in under half of cases. Mucocele, localized pseudomyxoma peritonei, benign tumours and most appendiceal carcinoids are cured by appendicectomy alone. Right hemicolectomy is indicated for: (1) invasive adenocarcinoma; (2) tumours close to the caecum; (3) lesions larger than 2 cm; (4) mucin production; (5) invasion of the lymphatics, serosa or mesoappendix; and (6) cellular pleomorphism with a high mitotic rate. Tumours of 1-2 cm, small mucinous carcinoids, adenocarcinoma confined to the mucosa, and tumours in children may be treated by appendicectomy alone at the surgeon's discretion. The 5-year survival rate associated with classical carcinoid is more than 90 per cent. The prognosis of mucinous carcinoid is intermediate between that of classical carcinoid and well differentiated adenocarcinoma. The prognosis of adenocarcinoma is determined by Dukes' stage and is similar, stage for stage, to that of colorectal carcinoma.

The application of receptor theory to receptor-binding and enzyme-binding oncologic radiopharmaceuticals

The successful imaging of tumor biochemistry using a receptor binding radiotracer is related to the affinity constant and the receptor concentration. The target to nontarget ratio can be predicted by steady state equations using in vitro data, although this is a necessary but not sufficient upper limit. The prediction of the sensitivity of the radiopharmaceutical to changes in the tumor biochemistry is not possible with this evaluation.

Expanding uses of octreotide

This chapter reviews the therapeutic use of octreotide in a variety of pancreatic disorders, including acute pancreatitis, in the prevention of postoperative and post-ERCP pancreatitis, in the control of postoperative pancreatic fistulae, and in chronic pancreatitis for the control of pain and of pseudocysts and ascites. The review also discusses the use of octreotide in intestinal disorders of motility, gastrointestinal bleeding, intestinal fistulae and refractory diarrhoea, including the diarrhoeas of AIDS, diabetes, short gut, chemotherapy, ileostomy and gastric surgery. The use of octreotide in neuroendocrine tumours, both for therapy and diagnostic imaging, is reviewed briefly. The paucity of adequately controlled studies in many of these situations is indicated and the potential usefulness of octreotide estimated.